Study On Engineering Properties Of Foamed Lightweight Soil Subgrade In The Soft Soil Foundation

As a new type of subgrade filler,foamed lightweight soil has some good engineering properties,such as lightness,high flow ability and conveniently installed.Therefore,foamed lightweight soil has been widely applied to highway engineering,and the engineering effect is preferably satisfactory,which can provide a new treatment method for soft soil foundation.In order to study its preparation technology,physical and mechanical performances,durability and microstructure,a series of laboratory tests of foamed lightweight soil are conducted by mathematical statistics method,while this paper relies on the first segment of Guangzhou-Foshan-Jiangmen Freeway in Jiangmen city as the supporting project.The main works are as follows:(1)Research on preparation technology of foamed lightweight soil is carried out on the basis of related specifications.By measuring qualitative indices of its raw materials,the mixture ratio of foamed lightweight soil can be designed,and the preparation method about foamed lightweight soil has been conducted.(2)Research on physical and mechanical performances of foamed lightweight soil are carried out on the basis of test samples.Firstly,the effects of water-solid ratio and fly ash content on physical and mechanical performances of foamed lightweight soil are analyzed by changing the water-solid ratio and the amount of fly ash.Secondly,the optimum mixture ratio of foamed lightweight soil can be obtained by measuring its flow value,density,and unconfined compressive strength.Finally,choosing some mixture ratio to conduct a series of laboratory tests of foamed lightweight soil in order to acquire the variation laws of water absorption,flexural strength,CBR,and rebound modulus.Besides,the equations between flexural strength,CBR and unconfined compressive strength are set up based on the mechanical analysis.(3)Research on durability of foamed lightweight soil is carried out on the basis of different external factors.Firstly,the fatigue performance of foamed lightweight soil is deeply analyzed by beam fatigue tests in order to simulate cyclic loading.At the same time,combining the general situation of the supporting project to forecast actual fatigue life of foamed lightweight soil.The results show that foamed lightweight soil as subgrade filler has good anti-fatigue performance under the cyclic loading.Secondly,the dry-wet cycle test and freeze-thaw cycle test are carried out to evaluate water stability and freeze-thaw stability.The results show that the anti-water and anti-frozen intensity loss rate are lower,which can illustrate the fact that foamed lightweight soil not only has good water stability but also good freeze-thaw stability.(4)Research on microstructure of foamed lightweight soil is carried out on the basis of different magnifications.The microstructure characters of foamed lightweight soil are scanned by electron microscope,and the results show that difference of water-solid ratio causes great changes in the organizational structure of foamed lightweight soil,especially in the amount,shape,and distribution of pores.